In the report out this week, the cost of using vinegar was found to be 3.6 times greater than glyphosate, and weeds treated by vinegar would reappear within a month instead of five to six months after being sprayed with the chemical weed-killer.

Reputation killer

Contractors added they were not willing to recommend the use of vinegar and "were concerned that complaints about its 'smell' would harm their reputation".

Councillor Anthony Negus said the trial "must be redone much more rigorously", describing the report as "patchy".

"Cost has to be a minor factor. If there is a real risk to health, that trumps everything," he said.

Community gardener Karen Sillence called on the council to "mobilise the public to help".

"There have to be other ways they haven't tried to clear weeds without using chemicals. I want to see them persevering."

A Bristol City Council spokesman said the authority would "now consider our options and continue to keep up to date with relevant research and emerging products and techniques, to see if we can find a better solution".